#include <iostream>
#include <algorithm>

using namespace std;

int main() {
    int x, y;
    cin >> x >> y;

    if (x > y) {
        swap(x, y);
    }

    int sum = 0;
    int i = x + 1;
    while (i < y) {
        if (i % 2) {
            sum += i;
        }
        i++;
    }

    cout << sum << endl;

    return 0;
}
